The present invention relates generally to sensor packages, and more particularly, to features of sensor packages for stress isolation.
Sensor packages utilize microelectromechanical systems (“MEMS”) (e.g., dies) to perform sensor functions. Multiple dies are simultaneously constructed on a silicon wafer. Individual dies are cut from the wafer and mounted to a circuit board to integrate sensors into the circuit. To protect the die and circuit board from damage and to provide an interface to the sensor, the die and circuit board are mounted within a sensor package.
Sensor packages have various configurations for supporting the die and circuit board. In some sensor packages, the die is bonded directly to the circuit board. Direct bonding of the die to the circuit board is economical, but leaves the die vulnerable to thermally-induced stress (e.g. thermal expansion of dissimilar materials and the like) and to mechanical-induced stress (e.g. external loads imposed on the sensor package and the like). In other sensor packages, dies are bonded to pedestals to isolate the die from thermally-induced and mechanically-induced stress. Within such packages, the die is bonded to pedestal that is larger than the die itself, and sometimes, the pedestal is constructed from a material with a similar coefficient of expansion to further isolate the die. Sensor packages used for precision sensors are typically hermetically sealed. In addition, the stress isolation features of the previously described sensor packages, the dies of hermetically sealed sensors are encapsulated within the package. Because of this additional measure of isolation, feedthrough features are added to transmit signals from the die through the hermetic barrier.
However, each configuration creates complexity and additional manufacturing. Therefore, many sensor packages use cheaper, less complex forms of stress isolation. The present invention, which is described in detail hereafter, reduces complexity and manufacturing cost while providing the stress isolation benefits of more complex and costly sensor packages.